Off-highway equipment such as trenchers and the like commonly use both hand and foot controls for adjusting a regulator of a prime mover. The hand control offers metered ground speed control during a work mode for the implement. The foot control is typically used during a transportation mode for the implement.
The regulator on such an implement typically includes a pivotal lever connected to a servovalve of a hydrostatic pump. Movement of the regulator lever in one direction from a neutral position conditions the speed and forward direction of the implement. Movement of the regulator lever in an opposite direction from a neutral position conditions speed and reverse direction for the implement.
The foot control of known control systems includes a self-centered foot pedal which is connected through a linkage assembly to the regulator. Pivotal movement of the foot pedal to opposite sides of a neutral position changes the position of the regulator and thereby conditions the implement as a function of the resultant regulator position. The foot pedal is normally maintained in a center or neutral position under the influence of a centering spring. As will be appreciated, using a spring influenced foot pedal to maintain a substantially constant speed for the implement over an extended time period can be a tedious process.
In view of the above, some implements have been known to use a hand control for conditioning the implement to operate in a substantially constant condition. With these known systems, the hand control is connected to the regulator through the same linkage assembly used by the foot control. Adjustment of the hand control, however, requires an operator to overcome the forces of the self-centering spring used to return the foot pedal to a neutral condition.
Connecting the hand control and foot control through the same linkage assembly has presented several drawbacks during operation of the implement. First, using a common linkage assembly for the hand and foot controls makes it difficult for the operator to achieve accurate metered control of the regulator through use of the hand control. Overcoming the spring forces acting to return the foot pedal to a neutral position requires considerable effort on the part of the operator thereby frustrating accurate metered operation of the regulator. Second, use of a common linkage assembly causes the foot pedal to move conjointly with the hand control. Thus, the foot pedal is prevented from automatically returning to its neutral position upon adjustment of the hand control. As will be appreciated, the cumulative movement of the regulator under the influence of the foot and the hand controls further needs to be governed to inhibit damage to the hydrostatic pump connected to and which operates in response to the position of the regulator.